Reactor is the core part of a nuclear power station, while the reactor control rod drive mechanism (CRDM) can lift, insert or keep the position of the control rod in the reactor core, and is used to control fission rate of the reactor, and realize starting and stopping the reactor and adjustment of reactor power; under accident conditions CRDM can also rapidly insert the control rod (rapidly dropping the rod), such that the reactor is urgently stopped in a short time to ensure safety. These functions can not be realized without CRDM electromagnetic coil assembly, due to its special operating environment and essential functions, it requires that the CRDM electromagnetic coil must have characteristics of high temperature resistance grade, excellent insulating property, radiation resistance, humidity resistance, shock resistance and the like.
For a long time, the temperature resistance grade of the CRDM electromagnetic coil assembly of the nuclear power station can only reach around 250° C. at most, while the temperature of the coolant in the reactor is above 300° C., so in practical applications the electromagnetic coil assembly can be cooled only through forced ventilation to ensure reliable operation of CRDM, which complexities the upper structure of the head cover of the reactor.
In the prior art, in order to make the CRDM electromagnetic coil assembly of the nuclear power station have better high-temperature resistance, those skilled in the art make many efforts, e.g. the technical scheme provided by invention patent application with Application No. CN201410500311.4 and titled “electromagnetic coil insulating structure as well as electromagnetic coil outer shell and outer shell inner bobbin” can improve high-temperature resistance of the CRDM electromagnetic coil assembly of the nuclear power station, but there are also other disadvantages. Performing further study with respect to high-temperature resistant CRDM electromagnetic coil assembly to optimize operating characteristic of CRDM and adapt to new requirements of CRDM with extra-long life, is the important direction of improvement of the existing reactor control rod drive mechanism.